This invention relates to newly identified polynucleotides, polypeptides encoded by such polynucleotides, and the use of such polynucleotides and polypeptides as part of a diagnostic assay for detecting the presence of prostate cancer and prostate cancer metastases. The polynucleotides and polypeptides of the present invention are human prostatic specific reductase, and are sometimes hereinafter referred to as xe2x80x9cPSRxe2x80x9d.
Carcinoma of the prostate has long been regarded as an unpredictable disorder which makes sound therapeutic decisions in evaluating the results of different types of treatment very difficult. Prostate cancer is unique among the potentially lethal human malignancies in that there is a wide discrepancy between the high prevalence of histologic changes recognizable as cancer and the much lower prevalence of clinical disease.
The concept that adenocarcinoma of the prostate exists in a latent and a clinical form is supported by epidemiologic, pathologic and clinical evidence. Although these divergent manifestations of prostate cancer have come in architectural and cytologic features, they can be distinguished from each other to some degree by differences in certain pathologic features, such as the volume, grade, and invasiveness of the lesion.
Prostate cancer has become the most common cancer among American men, and only lung cancer is responsible for more cancer deaths (Boring, C. C., Cancer Statistics, 41:19-36 (1991)). The age specific mortality rate has slowly increased over the past 50 years and in black American men is nearly double the rate found in white men (Carter, H. B., Prostate, 16:39-48 (1990)). Prostate cancer is responsible for nearly three percent of all deaths in men over the age of 55 years (Seidman, H., et al., Probabilities of Eventually Developing or Dying of Cancer-United States, 35:36-56 (1985)). Since the incidence of prostate cancer increases more rapidly with age than any other cancer, and the average age of American men is rising, the number of patients with prostate cancer is expected to increase dramatically over the next decade.
Approximately 30% of men with prostate cancer have distant metastases at the time of diagnosis (Schmidt, J. D., et al., J. Urol., 136:416-421 (1986)). Despite the impressive symptomatic response of metastases to hormonal manipulation (androgen deprivation), the survival rate for these patients is dismal: the median duration of survival is less than three years (Eyar, D. P., Urologic Pathology: The Prostate, Philadelphia, Pa., Lea and Febiger, 241-267 (1977)). By five years, over 75% and by ten years, more than 90% of these patients die of their cancer rather than with it (Silverberg, E., Cancer, 60:692-717 (1987) (Suppl.)).
The problem with prostate cancer is that many forms of prostate cancer are latent, in other words, are difficult to detect. Approximately 30% of the men over the age of 50 years who have no clinical evidence of prostate cancer harbor foci of cancer within the prostate (McNeal, J. E., et al., Lancet January, 11:60-63 (1986)). This remarkably high prevalence of prostate cancer at autopsy, seen in no other organ, makes it the most common malignancy in human beings (Dhom, G., J. Cancer Res. Clin. Oncol., 106:210-218 (1983)). There is strong support for the concept of multi-step process in the pathogenesis of prostate cancer in which latent cancers progress through some but not all of the steps necessary for full malignant expression (Utter, H. B., et al., J. Urol., 143:742-746 (1990).
There are a variety of techniques for early detection and characteristics of prostate cancers, however, none of them are devoid of any problems. Prostate cancer is a notoriously silent disease with few early symptoms. Symptoms associated with bladder outlet obstruction are commonly present in men over the age of 50 years and are often ascribed to benign prostatic hyperplasia (BPH).
Digital rectal examination (DRE) traditionally has been considered the most accurate test for the detection of prostate cancer. DRE has been demonstrated to be more sensitive, more specific, and to have a greater efficiency than a variety of laboratory tests available, however, few of these laboratory tests are still in clinical use today (Guinan, P., et al., N. Engl. J. Med., 303:499-503 (1980)). DRE detects cancer relatively late, and there is only a weak correlation between the size of the cancer estimated by DRE and the actual volume of cancer present. The most serious limitation of DRE is its lack of sensitivity (false-negative results). For example, approximately 10% to 20% of transurethral resections performed for benign prostatic hypertrophy in patients with no palpable abnormalities suggestive of cancer uncover an incidental cancer of the prostate. DRE detected only 12 of 22 cancers found in a screening study, while transrectal ultrasonography (TRUS) found 20 (Lee, F., et al., Radiology, 168:389-394 (1988)). Thus, DRE is relatively insensitive and nonspecific. Cancers detected by palpation are relatively large, late in their development and no longer curable, and some are very small, such that they are clinically unimportant cancers.
Patients having prostate cancer have an elevated prostate-specific antigen level. Cancer was detected in 26% of the men with a PSA level of 4.0 to 10.0 ng/ml. Serum PSA levels have been shown to correlate generally with the volume, clinical stage, and pathologic stage of prostate cancer, although there is a wide range of PSA values associated with any given volume or stage (Hudson, M. A., J. Urol., 142:1011-1017 (1989)). PSA, however, is not predictive of the features of the cancer in the individual patient. If the level of PSA is greater than 10.0 ng/ml, 57% to 92% of the patients will have locally advanced cancer. Therefore, while more specific, using a PSA level higher than 10 ng/ml may not offer an effective technique for early detection. There are other theoretical limitations to the use of this serum marker for early detection. A normal serum PSA level does not exclude the diagnosis of cancer. False-negative results are common, and a third of men treated with radioprostatectomy for prostate cancer have a normal serum PSA level. False-positive results are also common since PSA levels are often elevated in men with common benign conditions, such as BPH or prostatitis. In summary, PSA levels have proved to be extremely useful in the early detection of prostate cancer, especially when combined with DRE or TRUS. A PSA level detection, however, must be used in combination with DRE or TRUS in order to be sure that what is present is cancer and not BPH or prostatitis.
The introduction of TRUS has provided physicians with an effective way to see the internal anatomy and pathology of the prostate gland. TRUS has been used to screen for prostate cancer in several large series and has consistently been shown to increase detection when compared with DRE. TRUS is performed by taking a sonograph of the pelvic area and perhaps the most important use of TRUS in the early detection of prostate cancer is as a guide for directed needle biopsies of the prostate (Lee, F., et al., Radiology, 170:609-615 (1989)).
In accordance with one aspect of the present invention there is provided a method of and products for diagnosing prostate cancer metastases by determining the presence of specific nucleic acid sequences in a sample derived from a host.
In accordance with another aspect of the present invention, there is provided a method of and products for diagnosing a prostate disorder by determining an altered level of PSR protein in a biological sample derived from a host, whereby an elevated level of PSR protein indicates a prostate disorder diagnosis.
In accordance with another aspect of the present invention, there is also provided nucleic acid probes comprising nucleic acid molecules of sufficient length to specifically hybridize to the prostatic specific reductase genes and polypeptides of the present invention.
In accordance with a further aspect of the present invention, there are provided novel polypeptides which are prostatic specific reductase polypeptides, as well as biologically active and diagnostically or therapeutically useful fragments, analogs and derivatives thereof.
In accordance with another aspect of the present invention, there are provided isolated nucleic acid molecules encoding human PSR proteins, including mRNAs, DNAS, cDNAs, genomic DNAs, as well as biologically active and diagnostically or therapeutically useful fragments, analogs, and derivatives thereof.
In accordance with yet a further aspect of the present invention, there is provided a process for producing such polypeptide by recombinant techniques comprising culturing recombinant prokaryotic and/or eukaryotic host cells, containing human prostatic specific reductase nucleic acid sequences, under conditions promoting expression of said proteins and subsequent recovery of said proteins.
In accordance with yet a further aspect of the present invention, there are provided antibodies specific to such polypeptides.
In accordance with another aspect of the present invention, there are provided processes for using the PSR polypeptides of the present invention to screen for compounds, for example, antagonists and/or agonists and antibodies which interact with the polypeptides.
In accordance with yet another aspect of the present invention, there are provided antagonists to such polypeptides, which may be used to inhibit the action of such polypeptides, for example, in the treatment of prostate cancer.
These and other aspects of the present invention should be apparent to those skilled in the art from the teachings herein.